Particle therapy with magnetic resonance imaging

ABSTRACT

Particle radiation therapy and planning utilizing magnetic resonance imaging (MRI) data. Radiation therapy prescription information and patient MRI data can be received and a radiation therapy treatment plan can be determined for use with a particle beam. The treatment plan can utilize the radiation therapy prescription information and the patient MRI data to account for interaction properties of soft tissues in the patient through which the particle beam passes. Patient MRI data may be received from a magnetic resonance imaging system integrated with the particle radiation therapy system. MRI data acquired during treatment may also be utilized to modify or optimize the particle radiation therapy treatment.

CROSS-REFERENCE TO RELATED APPLICATIONS

The current application is a continuation of and claims priority under35 U.S.C. § 120 to U.S. patent application Ser. No. 16/570,810, filedSep. 13, 2019, which is a continuation of U.S. patent application Ser.No. 15/445,832, filed Feb. 28, 2017, which claims priority under 35U.S.C. § 119 to U.S. Provisional Patent Application No. 62/302,761,filed Mar. 2, 2016, the contents of each are hereby incorporated intheir entirety.

TECHNICAL FIELD

The subject matter described herein relates to devices, systems andmethods for particle radiotherapy treatment planning and administration.

BACKGROUND

Particle therapy uses beams of particles to kill cells to treat disease,typically proliferative tissue disorders such as cancer. Particletherapy can be used to treat targets in patients requiring a dose ofionizing radiation for curative effect, such as grossly observabletumors, anatomic regions containing microscopic disease or potentialdisease spread, or regions that include margins for motion and/ordelivery uncertainties. The ionizing radiation delivered by particletherapy beams destroys the DNA and other important components ofdiseased cells and prevents the cells from replicating.

Typical particle therapy involves treatment planning to determine how todeliver the prescribed radiation dose to the target, while at the sametime sparing healthy tissues in the vicinity by limiting doses belowacceptable thresholds to prevent deadly or debilitating side effects.Treatment planning often uses X-Ray computed tomography (CT) data todetermine the composition of the patient's body in conjunction withdeveloping the particle therapy treatment plan.

SUMMARY

In one aspect, described is a non-transitory computer program productstoring instructions that, when executed by at least one programmableprocessor forming part of at least one computing system, cause the atleast one programmable processor to perform operations. The operationscan include receiving patient radiation therapy prescriptioninformation, receiving patient magnetic resonance imaging (MRI) data,and determining a radiation therapy treatment plan for use with aparticle beam utilizing the patient radiation therapy prescriptioninformation and utilizing the patient MRI data to account forinteraction properties of soft tissues through which the particle beampasses. The patient magnetic resonance imaging data can be received froma magnetic resonance imaging device integrated with a particle radiationtherapy system.

In some variations, the influence of a magnetic field produced by an MRIsystem on the particle beam can be accounted for.

Determining the radiation therapy plan can include a determination of abiological effectiveness of dose delivered to the soft tissues by theparticle beam. The determination can be made through utilization of thepatient magnetic resonance imaging data.

X-ray computed tomography data can be received. Determining a radiationtherapy treatment plan can utilize the x-ray computed tomography data.

The operations can include receiving radiation therapy beam informationfor a radiation therapy treatment of a patient utilizing a particlebeam, receiving patient magnetic resonance imaging (MRI) data during theradiation therapy treatment, and, utilizing the patient MRI data toperform real-time calculations of a location of dose deposition for theparticle beam, taking into account interaction properties of softtissues through which the particle beam passes. The influence of amagnetic field produced by an MRI system on the particle beam can betaken into account in performing the real-time calculations of locationof dose deposition. The operations can include interrupting the particlebeam if the real-time calculations of the location of dose depositionindicate that dose deposition is occurring off-target. The operationscan include adjusting the energy of the particle beam if the real-timecalculations of the location of dose deposition indicate that dosedeposition is occurring off-target.

The patient MRI data and the real-time calculations of the location ofdose deposition can be utilized to modify a direction of the particlebeam in order to track a target. In some variations modifying thedirection of the particle beam can be performed through deflectionmagnets. In some variations, the patient MRI data and the radiationtherapy beam information can be utilized to calculate accumulated dosedeposition to the patient during the radiation therapy treatment.

The real-time calculations of a location of dose deposition can includea determination of a biological effectiveness of dose delivered to thesoft tissues by the particle beam through utilization of the patientmagnetic resonance imaging data. The radiation therapy treatment can bere-optimized based on the calculated dose deposition.

In one aspect a radiation therapy system is described. The radiationtherapy system can include a particle therapy delivery system fordelivery of radiation therapy to a patient via a particle beam. Theradiation therapy system can include a magnetic resonance imaging systemconfigured to obtain patient magnetic resonance imaging (MRI) dataduring radiation therapy. The radiation therapy system can include acontroller configured to receive the patient MRI data during radiationtherapy and utilize the patient MRI data to perform real-timecalculations of a location of dose deposition for the particle beam,taking into account interaction properties of soft tissues through whichthe particle beam passes.

The controller can be configured to interrupt the particle beam if thereal-time calculations of the location of dose deposition indicate thatdeposition is occurring off-target. The controller can be configured todetermine influence of a magnetic field of the magnetic resonanceimaging system on the particle beam in the calculations of the locationof dose deposition. The controller can be configured to determine abiological effectiveness of dose delivered to the soft tissues by theparticle beam through utilization of the patient magnetic resonanceimaging data.

The controller can be configured to interrupt the particle beam if thereal-time calculations of the location of dose deposition indicate thatdose deposition is occurring off-target. The controller can beconfigured to adjust the energy of the particle beam if the real-timecalculations of the location of dose deposition indicate that dosedeposition is occurring off-target. The controller can be configured toutilize the patient MRI data and the real-time calculations of thelocation of dose deposition to modify a direction of the particle beamin order to track a target.

The radiation therapy system can comprise deflection magnets. Themodification of the direction of the particle beam can be effectuatedusing the deflection magnets.

In some variations, the controller can be configured to utilize thepatient MRI data and particle beam information to calculate dosedeposition to the patient during the radiation therapy. The controllercan be configured to re-optimize the radiation therapy based on thecalculated dose deposition.

The radiation therapy system can include a dosimetry system. Thedosimetry system can be used for monitoring the radiation therapy to thepatient. The radiation therapy system can include a magnetic shieldingstructure surrounding at least a portion of the dosimetry system. Themagnetic shielding structure can include a plurality of shells. Theplurality of shells can be separated by an annular disk.

In some variations, the radiation therapy system can include a gantry.The gantry can be configured to allow delivery of the particle beam fromdifferent angles around the patient.

In some variations, the magnetic resonance imaging system can comprisetwo split main magnets. The radiation therapy system can include anisocenter. The two split main magnets can be separated by a plurality ofbuttresses located no further from the isocenter than an outer boundaryof the two split main magnets.

The details of one or more variations of the subject matter describedherein are set forth in the accompanying drawings and the descriptionbelow. Other features and advantages of the subject matter describedherein will be apparent from the description and drawings, and from theclaims. While certain features of the currently disclosed subject matterare described for illustrative purposes, it should be readily understoodthat such features are not intended to be limiting. The claims thatfollow this disclosure are intended to define the scope of the protectedsubject matter.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, show certain aspects of the subject matterdisclosed herein and, together with the description, help explain someof the principles associated with the disclosed implementations. In thedrawings,

FIG. 1 is a graph showing the penetrative depth of various exemplaryforms of radiation therapy into human tissue;

FIG. 2 is a flowchart for a method of radiation therapy treatmentplanning for particle radiation therapy, utilizing MRI data, that can beimplemented by software;

FIG. 3 is an illustration of a radiation therapy system having one ormore features consistent with the present description;

FIG. 4 is an illustration of a radiation therapy system having one ormore features consistent with the present description;

FIGS. 5A-5B illustrate a magnetic shielding system for shielding, forexample, a portion of a dosimetry system of a particle therapy system,having one or more features consistent with the current description;and,

FIG. 6 is a flowchart for a method of particle radiation therapytreatment having one or more elements consistent with the presentdescription.

DETAILED DESCRIPTION

Particle therapy is a form of radiotherapy using beams of energeticparticles for the treatment of disease, for example, cancer. Particlebeams can be aimed at a target within a patient and can cause damage tothe DNA and other important cellular components of the target cells,eventually causing the death of the cells. Cancerous cells have lessability than non-cancerous cells to repair radiation damage and aretherefore particularly susceptible to particle therapy. Depending on thecontext, “particle therapy” is sometimes used to refer to therapy withhadrons, such as protons, neutrons, antiprotons, mesons, etc., while itmay also refer to therapy utilizing ions or nuclei, such as lithiumions, helium ions, carbon ions, etc. Often, therapy with ions such ascarbon ions is said to be “heavy ion therapy,” although the line between“light ions” and “heavy ions” is not precisely defined. As used herein,the terms particle therapy, particle radiation therapy, particle beamand the like, refer to therapy utilizing hadrons as well as nuclei (orions). This terminology specifically excludes therapies such as photontherapy or electron-beam therapy.

FIG. 1 is a graph 100 showing the penetrative depth of various forms ofradiation therapy into human tissue. For a given energy, electron beamshave a low penetrative depth into human tissue (as shown by trace 102)compared to other radiation therapy forms. X-ray beams penetrate humantissue to a greater depth than electrons, but the dose absorbed bytissue falls off with the penetrative depth of the X-rays as shown bytrace 104. Particle therapy beams deposit more of their energy at aparticular depth into the tissue of the patient at the end of theirrange, as shown by trace 108. This depth near the end of their range maybe referred to as the Bragg Peak, shown as 108. A benefit provided byparticle therapy is that less energy is deposited into healthy tissueoutside of the target, thereby reducing the potential for damage to thehealthy tissue. Additionally, beyond the Bragg peak there is very littledose deposited compared to X-Ray beams.

Before particle radiation therapy can take place, a treatment plan mustbe generated. The present disclosure contemplates the use of magneticresonance imaging (MRI) data in a particular fashion in generating atreatment plan, which will have a predicted dose deposition closelymatching the actual dose delivered to the patient and closely matchingthe desired dose. X-ray computed tomography (CT) imaging data may alsobe employed to determine, for example, the mass density of the patient'stissues and regions of the patient that contain low and high densitytissues or regions such as lung, air, and bone. The analysis can beperformed for all particle beam paths.

A magnetic resonance imaging system can be employed to obtain MRI datathat, when analyzed, can more accurately determine the types of softtissues along beam paths to and through the target. Particle interactionproperties can then be determined from the MRI data, allowing for a moreaccurate determination of the dose delivered to the patient's tissuesand to the target. In addition, the MRI data can enable more accuratedetermination of the biological effectiveness of the particle beamtherapy.

The present disclosure contemplates that the MRI data may be combinedwith X-Ray CT data (for example, by using deformable image registration)to improve the accuracy of chemical composition and mass densitydetermination and thus improve the determination of particle therapydoses. If X-Ray CT data is not available, regions containing bone may bedetermined by ultra-short echo time (TE) MR imaging, while lung and airmay be determined from proton density weighted MR imaging.

X-Ray CT is well suited to produce a map of electron densities in thehuman body and is useful in determining dose delivered by photon beamradiation therapy because photons' dominant interaction probabilitiesare proportional to electron density. Electron densities are also wellcorrelated to mass density due to the fact that, for human tissues, theatomic numbers are low where nuclei have a fairly constant ratio ofneutrons to protons. CT Hounsfield numbers reflect the attenuationcoefficient of human tissues to X-rays. Thus, the Hounsfield number maybe identical for a variety of combinations of elemental compositions,elemental weights and mass densities, not to mention that the measuredHounsfield number may be inaccurate due to image beam hardening effectsand other artifacts. The uncertainty of elemental composition introducedwhen defining tissues using X-Ray CTs and Hounsfield numbers can causethe determined range of a particle beam to err significantly. This errorcan lead directly to dose computation errors, for example, becauseparticle stopping powers are required to accurately model dosedeposition along an energetic particle's path and to determine where theparticles reach the end of their range. Uncertainties in stopping powerdirectly translate into uncertainties in the location of the Bragg peak108, as illustrated in FIG. 1, which can move large dose regions off oftargets and tumors, failing to deliver an effective dose to thetreatment target and, instead, delivering particle radiation therapydose to healthy tissues that should be shielded from receiving highdoses of particle radiation.

Soft tissues have better contrast and definition when imaged with MRIsystems over X-Ray CT. As noted, X-Ray CT is excellent at determiningthe mass density of tissues with very different densities and thedefinition of regions containing air or cortical bone, due to its low orhigh contrast and low or high Hounsfield numbers. But, many soft tissueswill have very similar densities, with very different elementalcompositions. For example, tissues can have a fat-like (or adipose-like)nature or a water-like (or muscle-like) nature while having a verysimilar mass density, and hence such are hard to distinguish with X-RayCT data. Image noise, artifacts, and low contrast in X-Ray CT dataconspire to often misidentify tissue types with current methods. Interms of stopping powers, removing any density dependence, thedifference in stopping power between fat-like tissue (CH2) or water-liketissue (OH2) is dominated by the difference in atomic number between Oand C. For energies above tens of MeV/nucleon, as used in particletherapy, the ratio of stopping powers is significant.

Acquiring MRI data with pulse sequences that are sensitive to only wateror only fat, allows for the water-to-fat ratio of tissues to bedetermined through, for example, Dixon methods or sandwich echoes. Thedetermined water-to-fat ratios in the vicinity of the treatment targetcan then be employed to improve the knowledge of the elementalcompositions of the soft tissues. An MRI can obtain different“contrasts” by reading the signal of the excited protons at differenttimes and/or in different ways (the signal decays differently dependingon what type of molecule the hydrogen is attached to). It is thereforepossible to better differentiate different tissue types and deducechemical compositions utilizing an MRI.

The interactions (frequency and type of interaction) of a particle beamwith the tissues it is passing through depends on a number of factorsincluding beam particle type, particle energy, and the mass density andchemical composition of the tissue. Particle interactions, at least forcharged particles, include Coulomb interactions (i.e., electromagneticinteractions). Coulomb interactions almost always lead to a small energyloss of the incident particle and/or a small deflection in direction.Deflections, which cause the beam to spread out, are referred to asCoulombic scattering. The amount of energy lost per unit length may bereferred to as stopping power. The small energy losses that particlesexperience in Coulomb interactions are due to ionizations andexcitations of the atoms and molecules of the tissue. The frequency ofsuch interactions determines the ionization density along the path of aparticle. The higher the ionization density, the higher the probabilityfor cell damage. This is often measured with a quantity termed linearenergy transfer (LET).

Particle interactions also include nuclear interactions, which are lessfrequent than Coulomb interactions but are much more catastrophic. Theytend to result in the nucleus having been hit disintegrating intofragments (e.g., individual protons and neutrons, deuterons, tritons,lithiums, alphas, etc.). The type and number of such fragments depend onthe incident particle type and energy, and the nucleus that has beenhit. Nuclear interactions also leave behind radioactive nuclei, whichdecay and deposit additional dose.

Nuclear interactions and Coulombic scattering are highly dependent onatomic numbers of the nuclei. They both lead to broadening of a Braggpeak. For ions, nuclear interactions are also responsible for the tailof dose deposited beyond the Bragg peak. When there are heterogeneitiesin the beam path (e.g., air cavities, bones), Coulombic scattering leadsto a complex dose deposition structure behind the heterogeneity.

When the term interaction properties is utilized herein, it refers toany combination of interaction properties such as the Coulombicinteractions and nuclear interactions described above. Preferredembodiments of the present disclosure for, e.g., treatment planning orreal-time MRI guidance of radiation therapy, will utilize as manyinteraction properties as necessary in determining the location andquantity of dose deposition in patient tissues.

“Heavy ions” such as Carbon ions tend to have a much more devastatingeffect on cells than protons. Their nuclear interaction fragments havehigh LETs and tend to deposit their energy locally around theinteraction site. This is the main mechanism responsible for Carbon ionshaving a much higher “biological effectiveness” than protons. This leadsto both more cells being killed (or damaged) per unit energy depositedin the tissue for ions compared to photons, electrons and even protons.The energy deposited in tissue is referred to as absorbed dose, measuredin Gray (Gy). One Gy of absorbed dose from a Carbon ion beam will kill3-12 times more cells than one Gy of absorbed dose from a photon orelectron-beam, due to the differences in biological effectiveness.

With particle beam therapy, determination of the biologicaleffectiveness is beneficial or even required for proper treatment. Thereare a number of different ways to determine biological effectiveness.For example, the determination of a biologically effective dose (BED)aims to indicate quantitatively the biological effect of a particularradiotherapy treatment, taking into account numerous factors such as thetype of therapy, dose per fraction, dose rate, etc. In addition,relative biological effectiveness (RBE) is a ratio comparing theabsorbed dose for a particular mode of therapy to an absorbed dose forphoton therapy, where each dose leads to the same biological effect.

For protons, it has been assumed for years that RBE is constant ataround 1.1, but some have opined that this leads to suboptimal planningresults. Because the RBE for protons is so close to 1.0, neglecting toperform such a biological effectiveness calculation may not have toosignificant an effect on therapy but for neutrons, ions, mesons, etc.,RBE is much higher and can have a very significant effect on therapy ifnot taken into account.

To determine biological effectiveness, one needs to know the energyspectrum of the incident beam as well as the interaction properties ofthe materials or tissues that the beam passes through. Thus, preciseknowledge of the chemical composition of the tissues is absolutelyessential for accurate determinations of biological effectiveness. It isalso important to determine where the incident particle beam has lostthe majority of its energy (i.e., the Bragg peak). In addition,contributions to the dose distribution due to nuclear reactions,activation of tissues, time dose fractionation and cell damage vs.recovery can be incorporated into determination of biologicaleffectiveness. For these reasons, patient MRI data is important in thedetermination of biological effectiveness measures, similar to itsimportance in dose calculation and treatment planning.

MRI data can similarly be employed to allow evaluation of tissueelemental composition and accurate dose computation for the evaluationof the quality of a delivery plan before delivery. If the quality of thedose to be delivered is insufficient, the data collected at setup can beemployed to re-optimize a particle therapy treatment plan beforedelivery. This can be performed immediately prior to delivery of thetherapy, while the patient is on the treatment couch, or prior to thepatient's arrival for the actual treatment.

FIG. 2 is a flowchart for a method 200 of radiation therapy treatmentplanning for particle radiation therapy, utilizing MRI data, that can beimplemented by software, the method having one or more featuresconsistent with the present description. The software can be implementedusing one or more data processors that may be part of a systemcontroller. The software can include machine-readable instructions,which, when executed by the one or more data processors, can cause theone or more data processors to perform one or more operations.

In FIG. 2, at 202, patient radiation therapy prescription informationcan be received. Patient radiation therapy prescription information mayinclude data such as minimum dose required to a target tumor, maximumdose allowed to nearby organs of interest, or the like. The patientradiation therapy prescription information described herein is notintended to be limiting. The patient radiation therapy prescriptioninformation received at the radiation therapy treatment planning systemcan include prescription information typical for radiation therapytreatment planning.

At 204, patient MRI data can be received. In some variations, thepatient MRI data can be received from a magnetic resonance imagingdevice integrated with a particle therapy system. Patient MRI data mayencompass the region of interest for treatment, including, for example,a target treatment area of the patient and surrounding tissue thatradiation therapy beams may pass through and for which radiation doseshould be monitored. The MRI data may be taken before treatment at adifferent location from the treatment itself, or the MRI data may beacquired on the treatment table where an MRI is integrated with theparticle radiation therapy system.

At 206, a radiation therapy treatment plan can be determined for usewith a particle beam. The radiation therapy treatment plan can utilizethe patient radiation therapy prescription information and utilize thepatient MRI data to account for interaction properties of soft tissuesin the patient through which the particle beam passes. The radiationtherapy treatment plan can include, for example, the number of beams tobe utilized, the direction from which the beam(s) will be delivered, theenergy of the beam(s), collimator configurations, and the like.

Determination of the radiation therapy treatment plan can also accountfor the influence of the magnetic field of an MRI on the particle beam.This involves including the influence of the strong magnetic field ofthe MRI on transport of the ionizing radiation depositing dose in thepatient. The interaction cross sections are not strongly influenced bypolarization of spins as they compete with thermal effects (e.g., atbody temperatures only about four parts per million of spins are alignedwithin a 1 Tesla magnetic field), but the magnetic field exerts anexternal Lorentz force on moving charged particles that can be accountedfor to produce a more accurate dose computation.

Determination of the radiation therapy treatment plan can also includedetermination of a biological effectiveness of the dose delivered to thesoft tissues of the patient by the particle beam, through utilization ofthe patient magnetic resonance imaging data.

FIG. 3 is an illustration of a particle therapy system 300 having one ormore features consistent with the present description. To energizeparticles, the particles are first accelerated by a particle accelerator302. The particle accelerator can be a synchrotron, cyclotron, linearaccelerator, or the like. A synchrotron may be fed by either alow-energy cyclotron or a low-energy linear accelerator. The energy ofthe particle beam 304, prior to any downstream adjustment, determinesthe penetrative depth of the energized particles into the patient 306.Particle accelerators typically produce an energized particle beamhaving a defined energy. In some variations, the energy of the particlescan be reduced, for example, by running the beam through an attenuatingmedium. It is preferable for such to be done away from the patient dueto secondary neutrons that can increase unnecessary dose to the patient.The attenuating medium may be a wedge of material on a wheel or lineardrive that can be rotated to increase or decrease the energy. Themaximum energy is obtained by not applying any attenuating material inthe beam. The minimum is obtained by applying the thickest amount ofattenuating material in the beam. For a known material, a thickness canbe determined that would halt all energized particles from reaching thepatient to stop or interrupt the beam without deactivating the system.

Synchrotrons may also be configured to control beam energy by increasingor decreasing the number of passes through the accelerating elements inthe synchrotron ring. In principle, a linear accelerator can also changethe number of accelerating units, to a few fixed energies, over alimited range. Pulse to pulse energy changes are possible with theproper equipment.

In some variations, a particle therapy gantry 312 can be used to directthe energized particle beam 304 to the patient 306. The patient 306 canbe positioned on a couch 314 within the center of the particle therapygantry 312. The particle therapy gantry 312 can include gantryelectro-magnets 316 configured to direct the beam toward the patient306, through a dosimetry system 318.

The particle therapy gantry 312 can be configured to rotate tofacilitate delivery of particle therapy at different angles. In somevariations, the particle therapy gantry 312 can be configured to rotate360 degrees. One or more slip rings can be employed to facilitate thedelivery of electrical power to the electro-magnets other componentsdisposed on the particle therapy gantry 312. In some variations, theparticle therapy gantry 312 can be configured to rotate with a field ofrotation of approximately 360 degrees. In such variations, the particletherapy gantry 312 may rotate in one direction as far as it will go andthen rotate back in the other direction as far as it will go. Rotatingthe particle therapy gantry 312 around the patient 306 can facilitatedelivery of the energized particle beam 304 to the target at differentangles improving the sparing of healthy tissue and treatment planquality.

The particle therapy gantry 312 may include scanning beam magnets 320.The scanning beam magnets 320 can include, for example, pairs ofelectro-magnets. The pairs of electro-magnets can be arranged to havetheir magnetic fields in orthogonal planes to one another. The scanningbeam magnets 320 can be configured to manipulate the direction of theenergized particle beam 304. In some variations, scanning beam magnets320 can be configured to direct the energized particle beam in ascanning motion back and forth across the treatment target of thepatient.

In some variations, the system can include a fixed beamline 322. Thefixed beamline 322 can be configured to deliver the energized particlesdirectly to a patient through a dosimetry system 318, without a gantry.The system may also include one or more scanning beam electro-magnets320 configured to modify the direction of the energized particles of thefixed-line beam.

The particle therapy system may also include a scatterer. The scatterercan be configured to cause the energized particle beam 304 to scatteroutward. The system can also contain a beam wobbler or raster scanningmechanism to spread out the beam. The system can also include acollimator. The collimator can be a multi-leaf collimator comprising aplurality of thin metallic blades. The thin metallic blades can bemoveable, the position of which can be controlled by a computer. Thethin metallic blades can be configured to absorb the energeticparticles. The thin metallic blades can be arranged, by a controller,such that the shape of an aperture they form is complementary to thetarget within the patient. In this manner, the collimator can facilitateshielding of healthy tissue surrounding the target while permitting theenergized particles to penetrate to the target. In some variations, acollimator carved into a permanent shape may be used. Similarly, a boluscan be positioned in the path of the energized particle beam 304, whichmay be formed from a material semi-permeable to the energized particles,and may be carved to compliment the shape of the tumor.

FIG. 4 is an illustration of a radiation therapy delivery system 400having one or more features consistent with the present disclosure. Theparticle therapy delivery system 400 can have one or more elementssimilar to the elements of the system 300, illustrated in FIG. 3. Theradiation therapy system 400, according to the present disclosure, mayinclude a particle therapy delivery system for delivery of radiationtherapy to a patient via a particle beam, a magnetic resonance imagingsystem 402 configured to obtain patient magnetic resonance imaging (MRI)data during radiation therapy; and, a controller 424 configured toreceive patient MRI data during radiation therapy and utilize thepatient MRI data to perform real-time calculations of the location ofdose deposition for the particle beam(s), taking into accountinteraction properties of the soft tissues in the patient through whichthe particle beam passes.

The particle therapy delivery system 400 may have a split magnet MRI402. The split magnet MRI 402 can include two split main magnets 404 and406. The radiation therapy system can include an isocenter 407. The twosplit main magnets 404 and 406 can be separated by a plurality ofbuttresses 408. The plurality of buttresses 408 can be located nofurther from the isocenter 407 than the outer boundary of the two splitmain magnets 404 and 406. While the two split main magnets 404 and 406are each referred to as a single magnet, this terminology is notintended to be limiting. The two split main magnets 404 and 406 can eachinclude a plurality of magnets for the purpose of obtaining MRI data ofthe patient.

A split MRI system is illustrated in FIG. 4 for illustrative purposesonly. The MRI system used can be any type of MRI system. For example,the main magnets can include vertical open magnets, short bore magnets,magnets with a portal or thin section, or the like.

A couch 410 can be disposed within the split MRI system 402. The splitMRI system 402 can be configured to receive a patient 412, on the couch410, through the internal apertures of the two split main magnets 404and 406.

The split magnet MRI system 402, couch 410 and patient 412 can all bedisposed within a particle therapy gantry, such as gantry 312illustrated in FIG. 3. The particle therapy gantry may be configured torotate about the patient 412 delivering particle therapy to the patientfrom a multitude of angles.

The plurality of buttresses 408 can be disposed between the two main MRImagnets 404 and 406 and positioned within the outer periphery of the twomain MRI magnets 404 and 406 so as not to further increase the overalldiameter of the MRI system. The system may include, as an example, threebuttresses 408 spaced at equal angles around the two main MRI magnets404 and 406. The system can be operated such that the particle beam isdirected toward the patient between the split magnets and in a mannersuch that it will not travel through any of the buttresses 408.

The system can be configured to facilitate delivery of energizedparticles to the patient such that the energized particles are directedinto a gap 419 between the two main MRI magnets 404 and 406.

Particle therapy delivery system 400 can include a dosimetry system 416for monitoring the radiation therapy to the patient. The dosimetrysystem 416 can also include one or more components to facilitate thedelivery of particle therapy to the patient, for example, by providingfeedback to a controller.

The particle therapy delivery system 400 can include one or moremagnetic shielding structures 420 that may, for example, surround atleast a portion of the dosimetry system. Magnetic shielding structures420 can be configured to house electronic equipment that would otherwisebe adversely affected by the magnetic fields produced by main MRImagnets 404 and 406.

FIGS. 5A-5B illustrate an exemplary magnetic shielding structure 500 forshielding at least a portion of a dosimetry system 502 of a particletherapy delivery system, having one or more features consistent with thepresent disclosure. The magnetic shielding structure 500 may comprise aplurality of shells. The plurality of shells can be formed from a seriesof concentric shields configured to shield magnetic fields produced bythe split magnet MRI system 402 illustrated in FIG. 4. The concentricshields may be configured to surround at least a portion of a dosimetrysystem 502.

The magnetic shielding structure 500 can include a first shieldcontainer 504. The first shield container 504 can comprise a cylindricalbody portion 506 and an annular disk 508 disposed across one end of thecylindrical body portion. The annular disk 508 can include an aperture510 to allow the particles to pass through unhindered. In somevariations, the first shield container 504 can have a diameter ofapproximately seventeen inches. The diameter of the first shieldcontainer 504 can be selected to sufficiently house at least a portionof the components of the dosimetry system 502.

The magnetic shielding structure 500 can comprise a plurality of shells.For example 504, 512 and 514 in FIG. 5B, or the like. The plurality ofshells 504, 512, 514 can be nested together. At least one of theplurality of shells preferably includes an annular disk 516, 518, or thelike.

The magnetic shielding structure 500 may be positioned in a fixedlocation with respect to split magnet MRI system 402, or may beconfigured to rotate with a gantry, such as gantry 312 illustrated inFIG. 3. One or more structures can be disposed opposite or around thesplit magnet MRI system 402 and configured to mimic the magneticproperties of magnetic shielding structure 500 in order to minimizeinterference with the homogeneity of the MRI's magnetic fields.

The particle therapy delivery system 400, illustrated in FIG. 4, caninclude a controller 424. The controller 424 can be configured toelectronically communicate with the particle therapy delivery system300, as illustrated in FIG. 3, and to receive data from and control thesystem 400, as illustrated in FIG. 4. Controller 424 can also beconfigured to receive patient MRI data from the split magnet MRI system402 and to control the split magnet MRI system 402.

The controller 424 may be configured to utilize patient MRI data andparticle beam information to calculate dose deposition to the patientduring radiation therapy. The patient MRI data, along with informationabout the particle beam(s), can be used to calculate where, and to whatextent, dose is deposited into patient tissues over time. The actualdose depositions can be accumulated so that a total dose may be knownfollowing a particular fraction of treatment. This information can beused to re-optimize the treatment plan prior to a subsequent fraction oftreatment.

Furthermore, the calculated real-time dose deposition information may beutilized to improve or re-optimize the radiation therapy treatment planduring treatment delivery. Controller 424 may be configured to utilizesoftware to perform the real-time calculations of the location of dosedeposition. The software may include machine-readable instructions. Thecontroller 424 may include one or more data processors configured toexecute the machine-readable instructions. Execution of machine-readableinstructions, by the data processor, may cause data processor to performone or more operations, such as one or more of the operations describedin the present disclosure.

Controller 424 can be configured to calculate Bragg peaks for particlebeams relative to the location of a treatment target, utilizing thereceived MRI data. Controller 424 can be further configured to modifythe therapy beams in instances where it is determined that the Braggpeak(s) of the beams are not properly located with respect to thetreatment target.

As discussed with regard to treatment planning, real-time MRI data canbe used to determine the location of fat-like tissue and water-liketissue within the patient due to the MRI's ability to differentiatebetween the two. A water tissue-to-fat tissue ratio for the beam paththrough the patient can be determined to determine the interactionproperties of the patient's tissues in real time while the patient isundergoing treatment.

A particle interaction property map may be generated in real time toincrease the accuracy of the dose and range calculations. Determinationof the interaction properties of patient tissues with the energeticparticles in real time as the patient is being treated can facilitategreater accuracy and effectiveness in the delivery of particle therapy.Having a more accurate picture of the Bragg peak location relative tothe treatment target can allow positioning of the Bragg peak moreaccurately. This lends itself to increasing the radiation therapy dosageto the target, without an increased risk in radiating healthysurrounding tissue.

Controller 424 may also be configured to determine the influence of amagnetic field of the magnetic resonance imaging system on the particlebeam in calculating the location of dose deposition, as discussed above.

Controller 424 may further be configured to determine the biologicaleffectiveness of the dose delivered to soft tissues by the particle beamthrough utilization of the patient magnetic resonance imaging data.

The MRI data provided in real-time can also facilitate determination ofthe precise location and/or velocity of tissues along with prediction oftissue trajectories. This information can also be used to provide aprediction of where the treatment target will be so that the controller424 can cause the system 400 to deliver the particle beam to thatlocation.

Controller 424 may be configured to interrupt the particle beam if thereal-time calculations of the location of dose deposition indicate thatdose deposition is occurring off-target. The location of the treatmenttarget can be determined from MRI data obtained during the planningstages of the treatment. At the time of treatment, the location of thetarget may have changed due to changes in the patient's anatomy. Forexample, weight loss, a full stomach, gas, or the like, can cause arelative change in the location of the treatment target between imagingthe patient and delivering therapy to the patient. This increases therisk that the therapy will be less effective due to at least a portionof the treatment target not being irradiated and/or healthy tissue beingdamaged by the particle beam. Furthermore, a patient's voluntary orinvoluntary movements such as fidgeting, breathing, gas movement, andthe like can cause the location of the treatment area to move duringdelivery of the particle therapy to the patient. Real-time calculationsof the location of dose deposition can be used to cause controller 424to determine whether the dose is being deposited at its intended targetor whether the dose is off-target. If the dose is off-target, thecontroller 424 may interrupt the particle beam to avoid radiation doseto healthy tissues. The controller 424 may maintain the beaminterruption until the calculated location of dose deposition againcoincides with the target.

The controller 424 may be configured to adjust the energy of theparticle beam if the real-time calculations of the location of dosedeposition indicate that deposition is occurring off-target. If thereal-time calculations of the location of dose deposition indicate thedose is off target, especially if the dose is simply being depositedshort of the target or beyond the target, the controller may beconfigured to increase or decrease the energy of the particle beam sothat the location of the dose deposition will again coincide with thetarget. The energy of the particle beam may be modified at the source ordownstream from the source.

Controller 424 may be configured to utilize the patient MRI data and thereal-time calculations of the location of dose deposition to modify adirection of the particle beam in order to track a target. If thereal-time calculations of the location of dose deposition indicate thatthe dose is off target, especially if the aim of the beam is off targetlaterally (rather than the depth), the controller may be configured tomodify the direction of the particle beam so that the location of dosedeposition will again coincide with the target. For example, theradiation therapy system 400 can include deflection magnets 426,sometime called bending magnets or scanning beam magnets. The directionof the particle beam can be modified through the deflection magnets todeflect the trajectory of the beam using magnetic forces. The deflectionmagnets are typically electromagnets where the strength of the magneticforce generated by the electromagnets can be modified by applyingvarying amounts of electric current across the electromagnets.

FIG. 6 is a flowchart for a method 600 of radiation therapy treatmentfor particle radiation therapy, utilizing MRI data, that may beimplemented by software, the method having one or more featuresconsistent with the present description. The software can be implementedusing one or more data processors. The software can includemachine-readable instructions, which, when executed by the one or moredata processors, can cause the one or more data processors to performone or more operations. Method 600 is an example of the operations thatcan be performed by controller 424, as discussed herein.

At 602, radiation therapy beam information for radiation therapytreatment of a patient utilizing a particle beam can be received. Theradiation therapy beam information can include one or morecharacteristics of a particle beam. The one or more characteristics caninclude an indication of penetrative abilities of the particle beam, thespread characteristics of the particle beam, the number of particlebeams, or the like.

At 604, patient magnetic resonance imaging (MRI) data can be receivedduring the radiation therapy treatment.

At 606, the patient MRI data can be utilized to perform real-timecalculations of a location of dose deposition for the particle beam,taking into account interaction properties of soft tissues in thepatient through which the particle beam passes, as discussed herein. Theinfluence of a magnetic field produced by an MRI system on the particlebeam may also be accounted for in performing the real-time calculationsof location of dose deposition, as discussed above. And, a determinationof the biological effectiveness of dose delivered to the soft tissues bythe particle beam, through utilization of the patient magnetic resonanceimaging data, may also be performed in conjunction with the real-timedose calculations.

At 608, the particle beam can be interrupted if real-time calculationsof the location of dose deposition indicate that deposition is occurringoff-target.

In some variations, the energy of the particle beam can be adjusted ifthe real-time calculations of the location of dose deposition indicatethat deposition is occurring off-target. In other variations, thepatient MRI data can be utilized and the real-time calculations of thelocation of dose deposition to modify a direction of the particle beamin order to track a target.

While components have been described herein in their individualcapacities, it will be readily appreciated the functionality ofindividually described components can be attributed to one or more othercomponents or can be split into separate components. This disclosure isnot intended to be limiting to the exact variations described herein,but is intended to encompass all implementations of the presentlydescribed subject matter.

In the descriptions above and in the claims, phrases such as “at leastone of” or “one or more of” may occur followed by a conjunctive list ofelements or features. The term “and/or” may also occur in a list of twoor more elements or features. Unless otherwise implicitly or explicitlycontradicted by the context in which it used, such a phrase is intendedto mean any of the listed elements or features individually or any ofthe recited elements or features in combination with any of the otherrecited elements or features. For example, the phrases “at least one ofA and B;” “one or more of A and B;” and “A and/or B” are each intendedto mean “A alone, B alone, or A and B together.” A similarinterpretation is also intended for lists including three or more items.For example, the phrases “at least one of A, B, and C;” “one or more ofA, B, and C;” and “A, B, and/or C” are each intended to mean “A alone, Balone, C alone, A and B together, A and C together, B and C together, orA and B and C together.” Use of the term “based on,” above and in theclaims is intended to mean, “based at least in part on,” such that anunrecited feature or element is also permissible.

The subject matter described herein can be embodied in systems,apparatus, methods, and/or articles depending on the desiredconfiguration. The implementations set forth in the foregoingdescription do not represent all implementations consistent with thesubject matter described herein. Instead, they are merely some examplesconsistent with aspects related to the described subject matter.Although a few variations have been described in detail above, othermodifications or additions are possible. In particular, further featuresand/or variations can be provided in addition to those set forth herein.For example, the implementations described above can be directed tovarious combinations and subcombinations of the disclosed featuresand/or combinations and subcombinations of several further featuresdisclosed above. In addition, the logic flows depicted in theaccompanying figures and/or described herein do not necessarily requirethe particular order shown, or sequential order, to achieve desirableresults. Other implementations may be within the scope of the followingclaims.

What is claimed is:
 1. A radiation therapy system comprising: a particletherapy delivery system for delivery of radiation therapy to a patientvia a particle beam; a magnetic resonance imaging (MRI) systemconfigured to obtain patient MRI data; and a controller configured to:receive a radiation delivery plan for radiation therapy of the patientutilizing the particle beam; obtain the patient MRI data before deliveryof the radiation therapy; utilize the patient MRI data and the radiationdelivery plan to perform calculations of a location of dose depositionfor the particle beam, taking into account interaction properties ofsoft tissues through which the particle beam passes; determine abiological effectiveness of the dose deposition through utilization ofthe patient magnetic resonance imaging data; evaluate a quality of theradiation delivery plan utilizing the biological effectiveness;re-optimize the radiation delivery plan when the quality of the dosedeposition to be delivered by the radiation delivery plan isinsufficient; and control the particle therapy delivery system todeliver the radiation therapy based on the re-optimized radiationdelivery plan.
 2. The radiation therapy system of claim 1, wherein theobtaining of the patient MRI data is performed at setup while thepatient is on a treatment couch.
 3. The radiation therapy system ofclaim 1, wherein the obtaining of the patient MRI data is performedprior to delivery of the radiation therapy while the patient is on atreatment couch.
 4. The radiation therapy system of claim 1, thecontroller further configured to receive radiation therapy prescriptioninformation including one or more of a minimum dose required to a targettumor or a maximum dose allowed to nearby organs of interest, whereinthe evaluation of the quality of the radiation delivery plan furtherutilizes the radiation therapy prescription information.
 5. Theradiation therapy system of claim 1, the controller further configuredto take into account influence of a magnetic field produced by the MRIsystem on the particle beam in performing the calculations of thelocation of dose deposition.
 6. A non-transitory computer programproduct storing instructions that, when executed by at least oneprogrammable processor forming part of at least one computing system,cause the at least one programmable processor to perform operationscomprising: receiving a radiation delivery plan for radiation therapy ofa patient utilizing a particle beam; obtaining patient magneticresonance imaging (MRI) data before delivery of the radiation therapy;utilizing the patient MRI data and the radiation delivery plan toperform calculations of a location of dose deposition for the particlebeam, taking into account interaction properties of soft tissues throughwhich the particle beam passes; determining a biological effectivenessof the dose deposition through utilization of the patient magneticresonance imaging data; evaluating a quality of the radiation deliveryplan utilizing the biological effectiveness; re-optimizing the radiationdelivery plan when the quality of the dose deposition to be delivered bythe radiation delivery plan is insufficient; and controlling a particletherapy delivery system to deliver the radiation therapy based on there-optimized radiation delivery plan.
 7. The computer program product ofclaim 6, wherein the obtaining of the patient MRI data is performed atsetup while the patient is on a treatment couch.
 8. The computer programproduct of claim 6, wherein the obtaining of the patient MRI data isperformed prior to delivery of the radiation therapy while the patientis on a treatment couch.
 9. The computer program product of claim 6, theoperations further comprising receiving radiation therapy prescriptioninformation including one or more of a minimum dose required to a targettumor or a maximum dose allowed to nearby organs of interest, whereinthe evaluation of the quality of the radiation delivery plan furtherutilizes the radiation therapy prescription information.
 10. Thecomputer program product of claim 6, wherein the patient MRI data isreceived from an MRI system integrated with the particle therapydelivery system.
 11. The computer program product of claim 6, theoperations further comprising taking into account an influence of amagnetic field produced by the MRI system on the particle beam inperforming the calculations of the location of dose deposition.